Organic-matter enrichment in lacustrine rift basins reflects the interplay among paleoproductivity, preservation, and clastic dilution, but how these controls shift through rift evolution and respond to global carbon-cycle perturbations remains poorly understood. This study integrates organic and inorganic geochemical data from the Lower Cretaceous Aershan (K1ba) and Tengge'er (K1bt1 and K1bt2) formations in the Baorao Trough, Erlian Basin, northern China, to reconstruct paleoenvironmental evolution and identify the mechanisms governing differential organic-matter enrichment. Despite a progressive decrease in reconstructed paleo-water depth, source-rock quality improves upward from the syn-rift K1ba to the stable-late sag K1bt2 interval, with mean total organic carbon increasing from 0.90% to 1.84% and kerogen evolving from Type II1-II2 to Type I-II1. Three enrichment models are identified: (1) clastic-dilution-dominated, productivity-modulated for K1ba; (2) preservation-productivity dual-driven for K1bt1; and (3) low-dilution, productivity-sustained for K1bt2. The highest-quality source rocks occur in the shallowest K1bt2 rather than in the deep K1ba, challenging the assumption that maximum lake transgression coincides with optimal source-rock development. A +4.52‰ positive excursion in kerogen δ13C and +3.85‰ in bitumen δ13C from the upper K1ba, decoupled from thermal maturity, provides evidence for a terrestrial expression of the Valanginian Weissert Event. This signal is decoupled from organic-matter enrichment, indicating that the Weissert perturbation primarily affected continental weathering and carbon cycling rather than promoting anoxia-driven organic matter accumulation. These findings provide a predictive framework for source rock evaluation in small rift lakes and extend the terrestrial record of the Weissert Event into inland East Asia.

The Qiongdongnan Basin exhibits substantial heterogeneity in hydrocarbon composition and origin. Accurately characterizing this variation is critical for refining hydrocarbon generation models in marginal basins. The depositional facies of source rocks fundamentally control the composition and genetic types of hydrocarbons, yet this critical constraint remains poorly understood. To address this gap, biomarker profiling via GC-MS, and delta 13C analysis of individual n-alkanes, benzenes, and toluene via GC-IRMS were conducted on three major thermogenic accumulations. Results identify three distinct genetic gas types tied to depositional environments: (1) Y13 is coaltype gas derived from paralic facies source rocks with dominate higher plant input, deposited under oxygenated, non-stratified conditions; (2) L17 also exhibit coal-type gas, but was derived from terrigenous-marine facies source rocks deposited in a suboxic environment with reduced higher plant input; and (3) B21 represents oil-type gas derived from shallow marine facies source rocks deposited in suboxic-dysoxic setting with further reduce terrigenous input. All hydrocarbons originate from the Oligocene Yacheng Formation, with heterogeneity arising from spatially varying depositional facies within the basin, ranging from paralic in the west to shallow marine in the east, correlating with the earlier regional subsidence and marine transgression in the east. This faciescontrolled mechanism differs from traditional models that attribute gas variations to maturity, source rock intervals, or post-generation modification. This study provides a template for interpreting hydrocarbon compositions and genetic types, offering a refined framework for source rock evaluation and resource assessment in analogous marginal basins worldwide.

Deepwater shallow-layer exploration faces significant risks from unrecognized caprock failure, yet caprock integrity in such settings remains poorly understood due to low overburden stress and complex fluid dynamics. The Songnan Low Uplift in the Qiongdongnan Basin, South China Sea, offers a natural laboratory to investigate caprock failure mechanisms in shallow traps through integrated gas geochemistry, pressure-stress analysis, numerical simulations, and seismic interpretation.,Molecular and isotopic data indicate that natural gases in the Songnan Low Uplift are thermogenic coal-type gases from the Oligocene Yacheng Formation. Source correlation and migration modeling indicate that the YL8A gas field was charged primarily from the Baodao Sag, whereas YL8C received mixed contributions from the Lingshui, Songnan, and Baodao Sags. Carbon isotope kinetics constrain charging in YL8A to 9.5-2.3 Ma and in YL8C to 8.5-7.2 Ma, which coincides with the deposition of the Meishan Formation caprock. The YL13A structure, though currently water-bearing, once hosted a paleo-gas column of ~264 m, as evidenced by thermogenic gas shows (δ13C1: -48‰ to -44‰), elevated gas inclusion abundance (>5% GGI), seismic gas chimneys, and thermogenic gas hydrates. Pressure-stress analysis demonstrates that caprock failure occurred by hydraulic fracturing when pore pressure exceeded fracture pressure under hydrostatic conditions. The YL10A prospect shows similar pressure conditions that exceed the fracture threshold, indicating a high failure risk.,These findings challenge the conventional assumption that caprock failure requires overpressure, demonstrating that hydraulic fracturing can occur in shallow-buried deepwater traps under hydrostatic conditions. The quantitative caprock integrity assessment framework established here provides a practical tool for risk evaluation in deepwater shallow-layer exploration worldwide.

The platform margin belts of the Dengying Formation flanking the Deyang-Anyue rift trough represent a critical frontier for natural gas exploration and development in the Sichuan Basin.While giant gas fields,such as Anyue and Penglai,have been discovered along the eastern margin,the sedimentary characteristics of the western margin and the architectural disparities between the two flanks remain poorly understood,thereby constraining further exploration efforts in the region.By integrating core descriptions,well logs,and 3D seismic data,we systematically characterize the development of the Dengying Formation platform margins on both sides of the trough.Lithofacies paleogeographic maps were reconstructed for key intervals,and refined sedimentary facies models were established for the dual-flank system.As indicated by the research results(1)During the Late Sinian deposition of the Dengying Formation,the platform margins on both flanks primarily consisted of microbial mound,shoal,and mound-shoal complex facies,along with inter-mound/shoal subfacies,whereas the trough interior was dominated by slope-to-basin facies.(2)Distinct heterogeneities exist in the development and evolution of the platform margins.The eastern margin,controlled by basement faults,exhibits a steeply dipping,vertically stacked architecture with minimal lateral migration.In contrast,the western margin is characterized by multi-stage,gently sloping geometries with significant lateral migration distances.(3)Lithofacies paleogeographic mapping reveals substantial spatial variations in platform margin distribution between the second(Deng 2)and fourth(Deng 4)members of the Dengying Formation.During the Deng-2 period,the platform margin followed a quasi-circular distribution along the Chengdu-Suining-Zizhong trend.During the Deng-4 period,the platform margins expanded significantly,with the western margin trending NS along the Hongya-Jingyan-Zigong area and the eastern margin extending NS along the YantingSuining-Moxi area.Overall,the Deyang-Anyue rift trough is characterized by a"steep-east vs.gentle-west"and"single-stage-east vs.multi-stage-west"sedimentary facies model.

ABSTRACT The tectono‐sedimentary evolution of continental grabens is fundamentally governed by the differential kinematics of boundary faults. While classic models traditionally conceptualize grabens as symmetric structures, their actual evolution is profoundly asymmetric. Using the Sujiatun sag (Songliao Basin) as a natural laboratory, this study integrates 3D seismic, wireline log, and core data to reconstruct the high‐resolution sequence‐stratigraphic and tectono‐sedimentary dynamics of an asymmetric graben. We propose a comprehensive evolutionary model and elucidate the deep‐shallow coupled geomechanical drivers behind this asymmetry. The syn‐rift succession is partitioned into six third‐order sequences (SQ1–SQ6). During the initial rift phase (SQ1–SQ2), the dominant eastern key fault (F2) pinned the depocenter to the east, generating an aggradation‐dominated sequence filled by steep‐slope fan‐deltas. During the intensive rift phase (SQ3–SQ4), the conjugate fault system underwent a profound kinematic ‘see‐saw’ reversal. This tectonic switching drove a cross‐basin, westward migration of the depocenter, plunging the basin into a highly underfilled state dominated by deep‐lacustrine source rocks. In the recession phase (SQ5–SQ6), tectonic relaxation and geomorphological planation facilitated the basinward progradation of widespread, overfilled braid‐delta systems across a symmetrized basin profile. Geomechanical analysis reveals that initial fault differentiation stemmed from the selective reactivation of inherited basement fabrics. The subsequent kinematic reversal was dictated by the stress feedback of surface mass redistribution: massive sedimentary loading ‘clamped’ the eastern fault, whereas erosional unloading ‘unclamped’ the western fault. Macroscopically, asymmetric asthenospheric upwelling and magmatic underplating dictated the deep rheological heterogeneities driving the initial rupture. This ‘dynamic asymmetric graben’ model challenges static exploration paradigms, offering critical mechanistic insights into the heterogeneous distribution of source rocks and subtle lithostratigraphic traps, at the same time providing a robust predictive framework for hydrocarbon exploration in similar continental rifts worldwide.

Methyltrimethyltridecylchromans (MTTCs), molecular markers for paleosalinity reconstruction, have been widely found in sediments and crude oils from various origins and ages. However, the thermal stability of MTTCs remains ambiguous. In this study, the saturated and aromatic fractions were analyzed in a suite of oils exhibiting progressive thermal maturity from the Miaoxi area of the Bohai Bay Basin. The total concentrations of MTTCs in these oils decrease with increasing thermal maturity, reaching their lowest levels prior to the late oil window. The relative thermal stability of these alkylated compounds decreases with the degree of alkylation, which may result from their degradation via demethylation on the benzene ring. The position of the methyl group in dimethyl-MTTCs affects thermal stability, with an observed order of β-MTTC > ζ-MTTC > γ-MTTC. This corresponds to varying steric hindrance effects from different methyl positions on the benzene ring, leading to differential thermal stabilities among individual isomers. The β/γ-MTTC ratio can reflect changes in the thermal maturity of crude oils at the early mature stage. The α/δ-MTTC ratio and a cross-plot of MTTCI versus Pr/Ph ratios indicate that these oils, in which MTTCs survive, were derived from low-salinity source environments. Further sample analysis is required to determine whether thermal maturity influences the behavior of these proxies in paleosalinity assessments of oils from other sources. The findings of this study offer valuable insights into oil-oil and oil-source rock correlations, as well as paleoenvironmental diagnosis of early mature oils in which MTTCs are present.

As a strategic replacement area for hydrocarbon exploration in the Tarim Basin, the Kuqa Depression has been the subject of relatively limited research on the sedimentary characteristics of the Triassic strata within its western Wushi Sag, which constrains exploration deployment in this region. This study focuses on the Wushi Sag, systematically analyzing the sedimentary facies types, the evolution of sedimentary systems, and the distribution patterns of the Triassic Kelamayi and Huangshanjie formations. This analysis integrates field outcrops, drilling cores, wireline logs, and 2D seismic data, employing methodologies grounded in foreland basin theory and clastic sedimentary petrology. The paleo-geomorphology preceding sedimentation was reconstructed through balanced section restoration to investigate the controlling influence of foreland tectonic movements on the distribution of sedimentary systems. By interpreting key seismic profiles and analyzing vertical facies successions, the study classifies and evaluates the petroleum accumulation elements and favorable source–reservoir-seal assemblages, culminating in the prediction of prospective exploration areas. The research shows that: (1) The Triassic in the Wushi Sag mainly develops fan-delta, braided-river-delta, and lacustrine–shallow lacustrine sedimentary systems, with strong planar distribution regularity. The exposed strata in the northern part are predominantly fan-delta and lacustrine systems, while the southern part is dominated by braided-river-delta and lacustrine systems. (2) The spatial distribution of sedimentary systems was demonstrably influenced by tectonic activity. Paleogeomorphological reconstructions indicate that fan-delta and braided-river-delta sedimentary bodies preferentially developed within zones encompassing fault-superposition belts, fault-transfer zones, and paleovalleys. Furthermore, Triassic foreland tectonic movements during its deposition significantly altered basin configuration, thereby driving lacustrine expansion. (3) The Wushi Sag exhibits favorable hydrocarbon accumulation configurations, featuring two principal source–reservoir assemblages: self-sourced structural-lithologic gas reservoirs with vertical migration pathways, and lower-source-upper-reservoir structural-lithologic gas reservoirs with lateral migration. This demonstrates substantial petroleum exploration potential. The results provide insights for identifying favorable exploration targets within the Triassic sequences of the Wushi Sag and western Kuqa Depression.

With the strengthening of exploration efforts in Bohai, lithologic traps have gradually become new exploration targets. The Luda 10-56 well area is a newly evaluated gas field dominated by lacustrine fan deposits in Bohai. Well exploration has confirmed that the lacustrine fan has complex rock physical properties and indistinct reflection characteristics. The lithologic sand body reservoir changes rapidly laterally. The distribution range of sand bodies and their internal connectivity relationships are very complex. With limited oil field data, seismic and geological approaches were combined to form a new workflow for detailed characterization of lacustrine fan reservoirs. First, sedimentary microfacies research was conducted based on seismic geomorphological feature analysis in paleoenvironmental settings, which provided favorable facies belts and qualitative predictions for reservoir prediction. Meanwhile, morphology inversion technology based on facies-controlled modeling was used for quantitative reservoir prediction. The purpose of facies-controlled reservoir prediction is to combine microfacies analysis (a genetic method) with inversion-rock physics (a numerical analysis method) to improve the accuracy of reservoir prediction. The above detailed characterization techniques laid a reliable foundation for early development plan research and also have guiding significance for the study of other similar lacustrine fans in the area.

Organic matter types, abundance, and thermal maturity were assessed based on organic geochemical data. Then, we provided insights into the source rocks' hydrocarbon-generating capacity and described the favourable reservoir types in the Ordovician units of the Sichuan Basin. The cross-plot of hydrogen Index (HI, mg HC/g Total Organic Carbon (TOC)) versus temperature of maximum generation (T (max), degrees C) shows that samples from the Houtan and Sanhui sections have very low HI values (12.05 < HI < 7.75 mg HC/g TOC). These samples suggest kerogen type IV, which does not generate hydrocarbons and is considered inert. Outcrop and core samples from the southeastern part of the Sichuan Basin have HI values ranging from 450 to 68.29 mg HC/g TOC and suggesting type IIb kerogens, which are oil and gas-prone. Tongzi-Honghuayuan section samples have TOC, vitrinite reflectance (VRo), and T (max) values ranging from 0.76 to 1.54 wt.%, 0.98% to 1.96%, and 398 degrees C to 559 degrees C, respectively, which are above the defined lower TOC limit of effective source rock and in the dry gas window. Samples from the Late Ordovician Wufeng Formation have TOC values varying from 0.85 to 3.16 wt.%, in the dry gas generation window. The potential source rocks are mainly type IIb kerogens with TOC values higher than 0.5 wt.% and are in the oil window and dry gas window. In the investigated region, favourable source rocks are mainly from the Early/Middle Ordovician Meitan and the Late Ordovician Wufeng formations. Favourable reservoir areas are developed in three facies zones of the Tongzi, Honghuayuan, and Baota formations, including intra-platform shoal, platform marginal shoal, and palaeokarst areas around the Central Sichuan Uplift. The main reservoir spaces comprise intergranular pores, residual intergranular pores, dissolution pores, intergranular dissolution pores, and karst caves.

Upper Cretaceous continental lacustrine to deltaic depositional systems comprised the important petroleum reservoirs in the southern Songliao Basin, China, and their changes in depositional architecture reflected the interplay of tectonics, lake level change, and sediment supply. Based on integrated core, well logging, and seismic data, facies associations, depositional environments, depositional architecture, sequence stratigraphy, and their controlling factors in the lacustrine to deltaic depositional systems were systematically documented. Eleven facies associations were identified in the Nenjiang Formation. Two architectures of depositional systems, namely, deltaic depositional system, including digitate shallow-water delta, sheet shallow-water delta, deep- water delta, and lacustrine depositional system, were distinguished. Five fourth-order sequences (SQ1-SQ5) were recognized through the analysis of sequences bounded by logging curves and lithological characteristics, the intersection plot method of acoustic and resistivity curves, and seismic reflection characteristics. The SQ1 in the Nenjiang Formation was characterised by a normal cycle, whereas SQ2-SQ5 exhibited a reverse cycle pattern according to the changes in lithology and sand-to-land ratio. Shallow lacustrine, semi-deep and deep lacustrine deposits were developed in SQ1 and SQ2 and were characterised by thick hydrocarbon source rocks and a series of sublacustrine fans. SQ3 was dominated by digitate shallow-water delta deposits, with a sand body combination consisting of a subaqueous distributary channel in the upper part and a mouth bar in the lower part. Large-scale sheet shallow-water delta deposits were primarily located in SQ3-SQ5, with a sand body combination consisting of sand sheets and subaqueous distributary channels. The tectonic and climate caused changes in the direction of sediment supply, accommodating space and combination types of sand bodies, and thus, the depositional system shifted from lacustrine to deltaic. In conclusion, based on the integrated analysis of source rocks, faults, and sand bodies, the sublacustrine fans in SQ1 were likely to form lens-shaped lithologic hydrocarbon reservoirs, while the delta front sandstones of SQ3-SQ5 were prone to developing structural-fault, fault, and fault-lithologic hydrocarbon reservoirs.

The reservoirs in the Longwangmiao Formation of the central Sichuan Basin are typical examples of karstic dolomite reservoirs. However, there is still controversy regarding the dominant type of karst that controls reservoir development and the extent to which dolomitization modifies the reservoir. Based on extensive drilling and core data from the central Sichuan Basin, this study clarifies the distribution patterns of sedimentary facies and high-quality reservoirs within the studied strata. Through micro-scale in-situ geochemical analysis, this study investigates the influence of sedimentary and diagenetic processes on the formation of high-quality dolomite reservoirs. The analysis reveals that the Longwangmiao Formation contains two sedimentary sequences. The transgressive systems tract (TST) is dominated by low-energy mud-rich deposits, while the highstand systems tract (HST) has high-energy shoal and tidal flat environments with grainstones, packstones and crystalline dolostones. Reservoir rocks in the HST exhibit porosities of 5–10

For lacustrine shale oil and gas reservoirs with coexisting hydrocarbon fluid properties, evaluating the adsorption capacity of shale is of significant importance for the exploration of lacustrine shale oil and gas. Taking the lacustrine shale from the Jurassic Lianggaoshan Formation in the northern Sichuan Basin as an example, this study conducted pyrolysis, scanning electron microscopy (SEM), and high-pressure methane isotherm adsorption tests to investigate the methane adsorption capacity of lacustrine shale and its controlling factors. The research findings are as follows: (1) The organic matter content in the study area’s lacustrine shale is moderate, with organic types ranging from II to III, and it is within the oil generation window stage. The mineral composition exhibits characteristics of high clay and low silica content; (2) Both the TOC (total organic carbon) and clay minerals promote the methane adsorption capacity of lacustrine shale; however, due to the overall moderate–low TOC levels, the storage space is primarily composed of inorganic pores; (3) A high clay mineral content provides more surface area, becoming a primary factor influencing shale adsorption capacity. This indicates that semi-deep lake deposits also possess exploration potential.

Various data were utilized to analyze the sedimentary facies, completely reconstruct the palaeogeographic maps, and evaluate the reservoir quality of the Middle-Upper Cambrian Xixiangchi Formation in the Sichuan Basin, including evidence from field outcrops, drilling cores, microscopic thin sections, scanning electron microscopy (SEM), combined with experimental analysis data, such as petrophysical data (porosity (%) and permeability (mD)), and radioactive elements (uranium (238U), thorium (232Th), and potassium (40K)), and isotopic data (d13C)). In the Sichuan Basin, the Middle-Upper Cambrian Xixiangchi Formation was principally deposited in a restricted platform with a lithology predominantly composed of dolomite, with local occurrences of limestone and other rock types in small thicknesses. Graded beddings, cross beddings, horizontal beddings, storm depositions, and mud cracks locally developed in some samples. Four 3rd-order sequences (SQ1-SQ4) were identified within the Xixiangchi Formation in this study. Each sequence is subdivided into a highstand systems tract (HST) and a transgressive systems tract (TST). Reservoirs are principally developed in high-energy grain shoal deposits located in SQ2 and SQ3, with a minor occurrence in SQ1 and SQ4. The lithology of these shoal deposits is essentially composed of sandy dolomite and crystalline dolomite characterized by relatively low average porosity (2.61 %) and permeability (1.0073 mD) values. The increase of these values in several studied samples might be related to seepage and connecting dissolution pores and vugs through superimposed supergene karstification and bedding karstification highly improved the reservoir's

The marine–continental transitional shale of the Upper Permian Longtan Formation in northern Guizhou is an important source rock in the upper Yangtze region of China, and it holds significant potential for the exploration of shale gas. To investigate the correlation between sedimentary conditions and the accumulation of organic matters in marine–continental transitional shale, this paper performed an extensive analysis using organic geochemical testing, organic petrology examination, a cross-section polisher–scanning electron microscope (CP-SEM), and geochemical analysis. The Jinsha and Dafang drilling cores were selected as the research subjects. The results showed that the TOC of the Longtan Formation in the study area was relatively high, and the TOC content of the tidal flat–lagoon environment (average of 8.37%) was significantly higher than that of the delta samples (average of 2.77%). The high content of Al2O3 (average of 17.41% in DC-1, average of 16.53% in JC-1) indicated strong terrigenous detrital input. The proxies indicated that the Longtan Formation shale in northern Guizhou was deposited in a climate that was both warm and humid, with oxic–dysoxic sedimentary water characterized by high biological productivity and a rapid sedimentation rate. The organic-rich shales during the marine and continental transitional phases were affected by various factors, including the paleo-climate, water redox properties, paleo-productivity, sedimentation rate, and other variables, which directly or indirectly impacted the availability, burial, and preservation of organic matter.

The uniaxial compressive strength (UCS) of rocks is a critical index for evaluating the mechanical properties and construction of an engineering rock mass classification system. The most commonly used method for determining the UCS in laboratory settings is expensive and time-consuming. For this reason, UCS can be estimated using an indirect determination method based on several simple laboratory tests, including point-load strength, rock density, longitudinal wave velocity, Brazilian tensile strength, Schmidt hardness, and shore hardness. In this study, six data sets of indices for different rock types were utilized to predict the UCS using three nonlinear combination models, namely back propagation (BP), particle swarm optimization (PSO), and least squares support vector machine (LSSVM). Moreover, the best prediction model was examined and selected based on four performance prediction indices. The results reveal that the PSO–LSSVM model was more successful than the other two models due to its higher performance capacity. The ratios of the predicted UCS to the measured UCS for the six data sets were 0.954, 0.982, 0.9911, 0.9956, 0.9995, and 0.993, respectively. The results were more reasonable when the predicted ratio was close to a value of approximately 1.

At present, there is no precedent for reconstruction of Volatile Oil Reservoir into Underground Gas Storage (UGS) at home and abroad. Utilizes oil reservoirs to rebuild gas storage can fully utilize the mechanisms of gravity, miscibility, viscosity reduction, and imbibition, which can greatly enhancing crude oil recovery and gradually collabo-rate to build gas storage. This is a new approach to the rapid development of gas storage construction in China. Taking M Block in Jidong Oilfield as an example, The study starts from the geological characteristics of the reservoir, Analyzes the sealing condition, reservoir property, fluid feature and well productivity. Study results show that Es1 formation of the study area yield excellent reconstruction condition for its great sealing property, medium to high permeability, high productivity, no obvious interlayer and good internal connectivity, Furthermore, study also indicates there contain low hydrogen sulfide content. In response to the collaborative needs of gas drive oil recovery and UGS construction, Adopts the construction and operation mode of “initial top mild gas injection + pressure recovery → differential gas drive + efficient collaborative oil production → enhanced injection and production + long-term liquid carrying”. The UGS will be operated in pressure range of 17.5–40.0 MPa, with a effective storage capacity of 18.6 × 108 m3, constructs a three-dimensional injection and production well network of “high injection and low production, horizontal and vertical differentiation injection and production”, gradually form and expand secondary gas cap by gas injection and oil drainage in batches and stages, the study area is designed to be reconstructed with a mixed well pattern of 7 directional wells and 3 horizontal wells, Meets the effective control of gas storage capacity and the demand for unbalanced peak shaving gas production. It is estimated that the maximum production rate may yield 956 × 104 m3 and, the working gas may reach 9.0 × 108 m3, which is 48.4

Shallow-water deltas serve as a critical area for the exploration and development of terrestrial lacustrine oil and gas reservoirs. Current research on oil and gas exploration and development in China’s terrestrial lacustrine basins primarily focuses on their delta front facies zones. Despite extensive discussions on the sedimentary characteristics of shallow-water deltas by predecessors, there is a lack of comprehensive analysis on the combined effects of dynamic factors such as climate change, lake level fluctuations, and sediment supply. This paper, through a detailed examination of 12 core samples and integrating data from 493 exploratory, appraisal, and development wells in the study area, establishes a stratigraphic correlation framework using well–seismic integration techniques. It identifies two main sedimentary facies types in the southern Da’anbei area of the Songliao Basin: shallow-water deltas and lake facies, which can be further subdivided into four sub-facies and nine microfacies. Two depositional models for the shallow-water deltas of the Southern Songliao Nenjiang Formation are established: a deeper water background with channel-river mouth bar sequences forming the delta front framework and a shallower water background with channel-sheet sand sequences forming the delta front framework. This paper also discusses the controlling effects of paleoclimate, sediment supply, and lake level changes on sedimentary evolution, providing a scientific basis for the exploration of lithologic oil and gas reservoirs in the Nenjiang Formation of the study area and the deployment of horizontal wells.

The strategy of integrating water injection and chemical additives in combining secondary and tertiary oil recovery techniques has been widely investigated in enhancing oil recovery efficiency. Nevertheless, there is a lack of sufficient evidence on the effectiveness of a mixture of cationic and nonionic surfactants combined with water injection techniques in enhancing recovery in the application of carbonate reservoirs. Therefore, it is particularly critical to explore the impact of this combination strategy in enhancing recovery in fractured carbonate reservoirs. The recovery enhancement effect can be assessed by conducting phase behavior experiments and determining interfacial tension and contact angle. Further, the effectiveness of specific surfactant ration solutions in enhancing recovery can be verified by performing drive-off experiments. The results show that low mineralization water and surfactants have a significant synergistic effect in enhancing the recovery efficiency of carbonate reservoirs, with the optimal ratio of cationic to non-ionic surfactants being 2.5:1. The optimized surfactant ratio is able to increase the recovery of carbonate reservoirs by 20% compared to the original recovery rate.

Seeking effective measures for the improvement of high-selenium and high-cadmium soils holds significant theoretical and practical importance for sustainable agricultural development. This paper focuses on conducting a site-specific soil survey in the characteristic agricultural product production area of Hefeng County, Enshi Prefecture, Hubei Province. Through field experiments, we compared 14 soil improvement methods across three techniques: chemical passivation remediation, agronomic regulation, and microbial remediation. The study investigated their impacts on rice Cd content, rice Se content, yield, and quality and conducted a comprehensive evaluation of the remediation effects of the different treatments. The experimental results indicate that (1) increasing the content of soil conditioners can enhance rice yields, with Treatment 14 showing the most significant increase, yielding an additional 257.3 kg per mu, representing a 55.62% increase. Treatment 12 also demonstrated a notable yield increase of 95.1 kg per mu, or a 20.55% increase. Lime, sepiolite, and shell powder can effectively reduce rice’s absorption of Cd. Treatment 9 resulted in the lowest Cd content in the rice, at 0.03 mg/kg, with a Cd reduction rate of 92%. The optimal application rates for this Cd reduction were 200 kg/mu of lime, 125 mL/mu of foliar inhibitor, and 50 kg/mu of carbon-silicon fertilizer. Treatment 12 achieved a rice Cd content of 0.11 mg/kg, with a 70% reduction in Cd, bringing the rice Cd content down to below 0.2 mg/kg, which meets the requirements of the National Food Safety Standard: Maximum Levels of Contaminants in Foods. In the comprehensive scoring of all treatments, considering four evaluation indicators—rice Cd content, rice yield, rice quality, and cost—Treatment 12 (300 kg/mu of soil conditioner + 50 kg/mu of carbon-silicon fertilizer) was found to be the optimal treatment through comparative scoring. It demonstrates good potential for ensuring safe rice production and can serve as a reference standard for repairing Cd-contaminated rice paddies in the local area, with promotional value.